Creation of Hot Summer Years and Evaluation of Overheating Risk at a High Spatial Resolution under a Changing Climate

Abstract

It is believed that the extremely hot European summer in 2003, where tens of thousands died in buildings, will become the norm by the 2040s, and hence there is the urgent need to accurately assess the risk that buildings pose. Thermal simulations based on warmer than typical years will be key to this. Unfortunately, the existing warmer than typical years, such as probabilistic Design Summer Years (pDSYs) are not robust measures due to their simple selection method, and can even be cooler than typical years. This study developed two new summer reference years: one (pHSY-1) is suitable for assessing the occurrence and severity of overheating while the other (pHSY-2) is appropriate for evaluating the thermal stress. Both have been proven to be more robust than the pDSYs. In addition, this study investigated the spatial variation in overheating driven by variability in building characteristics and the local environment. This variation had been ignored by previous studies, as most of them either created thermal models using building archetypes with little or no concern about the influence of local shading, or assumed little variation in climate across a landscape. For the first time, approximately a thousand more accurate thermal models were created for a UK city based on the remote measurement including building characteristics and their local shading. By producing overheating and mortality maps this study found that spatial variation in the risk of overheating was considerably higher due to the variability of vernacular forms, contexts and climates than previously thought, and that the heat-related mortality will be tripled by the 2050s if no building and human thermal adaptations are taken. Such maps would be useful to Governments when making cost-effective adaptation strategies against a warming climate.